Bearing arrangement for rolling cutter

ABSTRACT

The specification discloses an excavating tool in the form of a rolling cutter in which a tubular outer body is mounted on an inner journal or core member and bearings are provided between the core member and the body in the form of axially spaced roller bearings and a row of balls between the roller bearings. The races for the balls are not circular in cross section, but are formed to a lesser curvature than the balls and engage the balls on opposite sides of the central radial plane of the row of balls.

United States Patent [191 Rumbarger Oct. 2, 1973 1 1 BEARING ARRANGEMENTFOR ROLLING CUTTER [75] lnventor: John H. Rumbarger, Wayne, Pa.

[73] Assignee: Subterranean Tools Inc., Beaumont,

Tex.

[22] Filed: May 17, 1971 [21] Appl. No.: 144,122

[52] US. Cl. SOS/8.2, 175/372 [51] Int. CL... F16c19/49, F16c 27/04,F16C 33/58 [58] Field of Search 308/82, 196, 216, 308/235; 175/372 [56]References Cited UNITED STATES PATENTS 1,437,834 12/1922 Buckwalter308/215 2,120,154 6/1938 Schildgen....

2,759,243 8/1956 Smith 308/196 X 3,447,394 6/1969 Wagner et a1. 308/196X FOREIGN PATENTS OR APPLICATIONS 946,559 6/1949 France 308/215 PrimaryExaminer-Charles J. Myhre Assistant Examiner-Barry GrossmanAttorneyMelvin A. Crosby [57] ABSTRACT The specification discloses anexcavating tool in the form of a rolling cutter in which a tubular outerbody is mounted on an inner journal or core member and bearings areprovided between the core member and the body in the form of axiallyspaced roller bearings and a row of balls between the roller bearings.The races for the balls are not circular in cross section, but areformed to a lesser curvature than the balls and engage the balls onopposite sides of the central radial plane of the row of balls.

3 Claims, 3 Drawing Figures PAIENTEB OCT 2 I975 INVENTOR. JOHN RUMBARGER&BY

ow 70E BEARING ARRANGEMENT FOR ROLLING CUTTER This invention relates toexcavating toolsandisparticularly concerned with a rolling cutter'of thetype employed for boring operations, such as in raise boring or intunnel boring.

Rolling cutters of the nature referred Y to a'are'well known andcomprise a central journal or core member on which is rotatably mounteda body member that is provided with ribs or protuberances or 'hardinserts-so that when the body is pressed against formation and rolledthereover, the formation will be reduced by breaking and crushing.

The service to which such roller cutters are subjected is severe withextremely high pressure peaks and shock loads being imposed thereon. Thebearings which'journal the body on the journal or core member or thusoperating under such conditions thatthey can deteriorate quite rapidly,and the life of the bearings in sucha' roller cutter has alwaysrepresented a problem.

With the foregoing in mind, the primary object ofthe present inventionis the provisionof a bearing arrangement for supporting a roller cutterbodyon the journal therefor which will have increased life overwhat'hasbeen obtainable heretofore.

Another object is the provision of a bearing arrangement for supportinga rolling cutter body on a core or journal member in which relativeaxial movement between the body and journal member is limited.

Still another object is the provision of a bearing arrangement of thenature referred to which can be'preloaded and which has shock absorbingcharacteristics.

These and other objects and advantages 'of the present invention willbecome more apparent upon reference to the following detailedspecification taken in connection with the accompanyingdrawingsin'which:

FIG. 1 is a fragmentary longitudinal section through a cutter embodyingthe features of the present invention;

FIG. 2 is a view showing a typical roller used in the cutter; and

FIG. 3 is a schematic view showing the manner in which the novel bearingrace configuration for the bearing balls of the cutter are formed.

BRIEF SUMMARY OF THE INVENTION The rolling cutter of the presentinvention has a central journal or core member adapted for 'beingmountedon a supporting shaft and a body member surrounding the core member.Axially spaced tubular rollers are interposed between the core memberand the body'memher in a central row of balls located axially betweenthe rollers is also provided.

The races which the balls engaged are formed somewhat in the manner of aGothic arch so that each ball engages the races at points angularlydisplaced on opposite sides of the central radial plane of the row ofballs thereby imparting axial stability to the support which the bearingarrangement provides for the rotatable body.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings somewhatmore in detail, the excavating tool, or cutter, comprises an outerrotatable body part I which may be tapered; as shown, but which may havea cylindrical or ribbed outer configuration; if so desired. Thebody-part I0 is provided with a 'bo'ree'xtending axiallythere'throu'ghand received in the -'bore is a journal, or core,'m'ember I2 which isalso'hollow and which is mounted on a central supportshaft l4. The'borein the body part and the container of the 1 coremember increase indiameter from one end to the legs at'the ends ofthe cutter assembly or aU shaped bracket having upstanding legs between which the cut-'terassembly "is mounted.

The bracket for the cutter is provided to enable the cutter-to bemounted on a suitable support which will support the cutter assemblywhile urging it against a formation to-be reduced while also rotating sothat the *body'part' I0'of the cutter assembly rolls on the formation ina conventional manner.

The journal member 14 is provided with a pair of radially outwardlyfacing roller paths l6 and 18 and directly opposed thereto on the insideof cutter body 10 are corresponding roller paths 20 and 22. The journalmember-and body of the cutters are carburized in at "least the regionsof the aforementioned paths and ground smooth so that the races will besuitable for receiving therebetween rollers making up the rollerbearings of the cutter assembly. The roller races, or paths, in thejournal, or core, member are preferably recessed andare slightly longerthan the respective rollers.

'Between paths 1'6 and 20, there is disposed a series of rollers 24 andbetween paths l8 and-22, there is dis- *'posed a series of rollers 26.The rollers are confined with slight axial freedom of movement, up toabout 0.01 0 inches in the journal member 12 so as to be freely rollablethereon.

Each roller is about one inch in diameter and has a one-half inch boreextending axially therethrough as indicated at 28. The provision of thebore extending through each roller imparts a slight degree of resiliencethereto'which assists in preventingundue wear on the rollers ortheroller races as the cutter body is rolled on a formation.

Advantageously, as will be seen in FIG. 2, each roller has the endsrounded, as indicated at 30, and about the first one-fourth inch of eachroller at each end tapers inwardly toward the adjacent end of the rollerat an angle of about one-half degree.

The rollers may be of the same length but, advantageously, the rollers26 are about l'Ainches long and the rollers 24 are about 2 inches long.The rollers 26 are disposed on about a 6 inch pitch diameter andconstitute a series of 19 rollers, whereas rollers 24 are arranged on apitch diameter of nearly 7 inches and constitute a'set of 22 rollers.

Axially outwardly from the outer ends of the roller sets are sealelements 32 which prevent foreign matter, such as fine grit, fromgetting into the bearing space inside body 10 while retaining lubricanttherein for lubricating the bearings which support body 10 on journalmember 12.

About in the center of the length of body 10 and disposed between body10 and joumal member 12 is a set of balls 34 which may be Wainches indiameter and arranged on about a 6%inch pitch diameter with 14 ballsmaking up the set.

The balls 34 engage a race 36 provided in body at the radially outersides of the balls and engage a race 38 provided on journal member 12 onthe radially inner sides of the balls.

The balls are charged into the space between races 36 and 38 by availingof a loading plug 40 inserted in hole 42 provided in journal member 12.The plug is put in hole 42 from the inside of the journal member afterthe balls have been charged into the space between races 36 and 38.Loading plug 40 is supported against axial movement in the bore byengagement with radially inwardly facing shoulder 46 spaced radiallyoutwardly from shaft 14 and by snap ring 44. Seals 45 on plug 40 sealagainst lubricant leakage.

In use, plug 40 is disposed on the unloaded side of the I cutter bykeying sleeve 12 to shaft 14 and locating shaft 14 in the supportbracket.

A particular feature of the present invention is to be found in theconfiguration of races 36 and 38. These races are formed, as shown inFIG. 3, so that each of the said races is somewhat in the form of aGothic arch and consists of two intersecting arcs. In forming the races,the outer one of which is schematically illustrated in FIG. 3, each raceis ground in two parts, one on each side of the transverse plane passingthrough the center of the race, and each part of the race is ground to alarger radius than the radius of balls 34.

' As will be seen in FIG. 3, for a race for receiving llfiinch balls,the radius to which the portions of the race are ground will be about0.795 plus or minum 0.0005. The centers from which the two portions ofthe respective race are ground are offset from the point where thecenters of the balls rolling thereon will be disposed on opposite sidesof the center line, a distance equal to about 0.0779 plus or minus0.0002 of an inch.

In finding the centers about which each portion of the race is ground,reference lines disposed about 60 degrees on opposite sides of centerline are provided and these are extended beyond the ball center untilthe aforementioned spacing is arrived at. The points of engagement ofeach ball with the ball races will thus be located about 60 degrees awayfrom the radial central plane of the row of balls.

In grinding the inner race, namely, the race 38 formed in the journalmember 12, the same procedure is followed.

The cutter assembly according to the present invention thus has threerows of rolling elements, all of which are free of cages or separators.

Each journal of the series of balls 34 has four contact points forcarrying thrust and this makes for greater stiffness against axialmovement of the cutter body 10 on the journal member 12 than is obtainedwith conventional type ball races. Under axial loading of the cutters,only one side of the series of balls will be loaded at a time and, uponreversal of the thrust load, the opposite side of the row of balls isloaded. This results in substantially decreased axial movement under areversing thrust loading which might be encountered in use.

In conventional bearings, where balls run in deep grooves, reversingaxial loading of the cutter body might result in axial movement of thecutter body on the journal member on the order of about 0.015 to about0.025 inches. The arrangement of the present invention, under similarreversing loading, might result in an axial displacement of the cutterbody of only about 0.007 inches total axial movement.

The reduction in axial movement of the cutter body on the journal membersimplifies seal design and assists in eliminating leakage andmisalignment problems that can result in rapid wear of seals and evenfailure thereof.

The hollow cylindrical rollers also provide an increased performancelife because the rollers can be assembled between their respective raceswith much closer clearance control. In fact, since the rollers are atleast slightly resilient, light diametral preloading of the rollers canbe accomplished and this permits the rows of rollers to carry a largerproportion of the external load than has heretofore been possible and,in this manner, the radial load component on the central row of ballscan be reduced and the life thereof significantly increased.

The use of hollow rollers also significantly reduces the overall springrate of the roller bearing row, up to an amount of about 50 per cent.

Still further, the hollow rollers tend to act as shock absorbers andshock loading of rolling cutters is the rule rather than the exceptionwhen such cutters are in use. The relatively resilient rollers deflectsomewhat when loaded, and the average dynamic or shock loadingtransmitted to the supporting structure is, thus, appreciably reducedwhen resilient hollow rollers are employed.

Modifications may be made within the scope of the appended claims.

What is claimed is:

1. In an excavating tool of the roller type; a tubular core or journalmember adapted for mounting on a support shaft, a tubular bodysurrounding said core member in closely spaced relation thereto, axiallyspaced roller paths formed on the outer periphery of said core memberand On the inner periphery of said body and radially resilient tubularrollers disposed in radially prestressed condition in the radial spacebetween said paths to journal said body on said core member, a row ofsolid balls between said core member and said body located axially aboutmidway between said roller paths, annular ball paths formed on said coremember and said body to engage said balls, said ball paths when viewedin cross section being formed of intersecting arcs having less curvaturethan that of said balls, each of said arcs extending over a range ofabout degrees on one side of the radial plane of said row of balls, andeach of said arcs having the center of curvature so located that thepoints of contact of each ball with the arcs is removed an angulardistance of about 60 degrees about the ball from the radial plane of therow of balls.

2. An excavating tool of the roller type according to claim 1 in whicheach said roller on the outside has a cylindrical central region andtapers inwardly at each end.

3. An excavating tool of the roller type according to claim 1 in whichthe roller paths formed on said core member are in the form of radiallyoutwardly opening annular recesses with radial end walls, said end wallsbeing axially spaced a distance greater than the axial length of therespective rollers.

1. In an excavating tool of the roller type; a tubular core or journalmember adapted for mounting on a support shaft, a tubular bodysurrounding said core member in closely spaced relation thereto, axiallyspaced roller paths formed on the outer periphery of said core memberand on the inner periphery of said body and radially resilient tubularrollers disposed in radially prestressed condition in the radial spacebetween said paths to journal said body on said core member, a row ofsolid balls between said core member and said body located axially aboutmidway between said roller paths, annular ball paths formed on said coremember and said body to engage said balls, said ball paths when viewedin cross section being formed of intersecting arcs having less curvaturethan that of said balls, each of said arcs extending over a range ofabout 90 degrees on one side of the radial plane of said row of balls,and each of said arcs having the center of curvature so located that thepoints of contact of each ball with the arcs is removed an angulardistance of about 60 degrees about the ball from the radial plane of therow of balls.
 2. An excavating tool of the roller type according toclaim 1 in which each said roller on the outside has a cylindricalcentral region and tapers inwardly at each end.
 3. An excavating tool ofthe roller type according to claim 1 in which the roller paths formed onsaid core member are in the form of radially outwardly opening annularrecesses with radial end walls, said end walls being axially spaced adistance greater than the axial length of the respective rollers.